Patent document 1: JP-A-58-19873
A rack-and-pinion type steering apparatus is generally comprised of a gear case, a pinion rotatably supported by this gear case through a pinion shaft, a rack bar on which rack teeth meshing with this pinion are formed, a rack guide disposed in the gear case to slidably support the rack bar, and a coil spring for pressing this rack guide toward the rack bar.
In such a rack-and-pinion type steering apparatus, in meshing portions of the pinion and the rack teeth of the rack bar, forces oriented in mutually opposite directions act in conjunction with the rotation of the pinion shaft, so that deflection occurs in the rack bar, and backlash in the direction of the row of rack teeth becomes large. As a result, knocking sounds are generated between the tooth portions of the rack teeth and the pinion. Therefore, there is provided a rack guide having a concave surface, generally a semicylindrical concave surface, which has a small frictional resistance at a side opposing the pinion shaft with respect to the rack bar. The concave surface of this rack guide is pressed against the rack bar by the resiliently pressing force of the coil spring. The arrangement provided is such that while the sliding frictional resistance with the rack bar is being reduced by bringing the concave surface of the rack guide into sliding contact with the rack bar, the backlash in the direction of the row of rack teeth is suppressed, to thereby reduce the knocking sounds at the meshing portions of the rack teeth and the pinion.